The work on this project will be concerned with the renal tubular active transport and renal metabolism of organic ions. Some of these substances are naturally occurring biologic substances (autopharmacologic agents) such as choline, catecholamines, prostaglandins and trimethylamine. Competitive inhibition of these transports by drugs, such as the inhibition of prostaglandin transport by probenecid is being studied. Such interactions have therapeutic implications. The magnitude and quality of renal metabolism of these substrates is under investigation. Renal N-oxidation of trimethylamine to trimethylamine oxide is a unique pathway.